The Essentialist Aspect of Naive Theories - Michael Strevens

4.2.2 Insides Versus Lineage in the Discovery Experiments
Recall from section 2.2 that the explanation of Keil’s discovery experiments
requires two hypotheses:
The lineage hypothesis: Children believe that members of a kind invariably
have offspring of the same kind, and
The insides hypothesis: Children believe that members of a kind invariably
have kind-specific insides.
Either hypothesis could explain children’s responses to the discovery experiments.
But in fact, they seem to play roughly equal roles in the explanation:
interviews with children during the experiments show that the children
appeal to lineage about as often as they appeal to insides to explain their
K-patterned inferences. I assume that this is because the two hypotheses
carry equal weight, on average, for the children. (It would be interesting to
conduct the experiment twice more, giving only information about lineage,
then only information about insides.)
Internal essentialism incorporates the insides hypothesis, but not the lineage
hypothesis. It follows that the internal essentialist child gets the relationship
between insides and kind for free, but must learn the relationship
between lineage and kind. According to internal essentialism, then, children’s
grasp of the relationship between insides and kind ought to come
earlier than their grasp of the relationship between lineage and kind. Why,
then, do the children in Keil’s experiment appeal to lineage as often as they
appeal to insides?
I consider three responses on behalf of the internal essentialist. The
first concerns timing: it may be that children learn about lineage at the
same time that they become essentialists. This suggestion squanders the
advantage that internal essentialism has over the other explanations of the
K-patterns: if children can learn about lineage at the same time that they
are becoming essentialists, surely they can learn about insides, too. Then
there is no motivation to incorporate the insides hypothesis (or any other
like it) in the essentialist hypothesis.
The second internal essentialist response is to attempt to incorporate the
lineage hypothesis in internal essentialism, that is, to posit that the beliefs
attributed by the lineage hypothesis are entailed by the child’s conception
of essence. It would have to be argued that it is a consequence of the child’s
conception of essence that organisms with a certain essence always have
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